The long term goal of this proposal is to train the applicant to become an independent academic physician- scientist studying the innate immune system and its impact on blood cancers. The principal investigator (PI) has completed PhD training focused on the cellular biology of natural killer (NK) cells, and MD training in internal medicine and hematology-oncology. This application describes a 5 year training program that will provide a mentored educational experience aimed at developing new scientific expertise in molecular profiling, massively parallel sequencing, proteomic analysis, manipulation of microRNAs (miRs), and the generation of mouse models. Dr. Timothy Ley will mentor the Pi's scientific and career development. He is a recognized leader in the field of lymphocyte cytotoxicity, in vivo genetic mouse models, and genomic analysis of leukemia. Furthermore, an advisory committee of medical scientist experts will provide additional scientific and and non-scientific career development guidance. The proposed research will evaluate the role of miRs in the regulation of NK cell cytokine activation. Recent work by the PI in Dr. Ley's laboratory identified two critical cytotoxic molecules, granzyme B (GzmB) and perforin (Prf1), that are post-transcriptionally regulated in NK cells. We hypothesize that miRs regulate GzmB and Prf 1 in resting NK cells, and that cytokine-activation releases their block in translation. To address this hypothesis, we propose the following specific aims: 1) We will define the miR expression profiles in resting and cytokine-activated NK cells, and evaluate candidate miRs that may regulate GzmB and Prfl mRNA translation. 2) We will define the mRNA (transcriptome) and protein (proteome) expression profiles of resting and cytokine-activated NK cells, integrate these databases to define the mode of regulation of molecules important during NK cell activation, and define the role of miRs for post-transcriptional regulation. Techniques utilized in the project include miR sequencing, miR microarrays, in vitro and in vivo manipulation of miRs, the generation of a NK cell-specific Cre mouse model, the generation of genetic mouse models deficient in miRs using Cre-Lox, and the global analysis of the NK cell transcriptome and proteome. Washington University provides an ideal setting to train physician-scientists, and will foster an invaluable mentored educational experience for the PI to realize his career goals in academic medicine. This overall career development proposal will train an independent physician-scientist for a lifetime of research studying the immune system and cancer. As NK cells are key components of immunity to numerous infectious pathogens, and are involved in the immuno-surveillance of malignancy, the research proposed may have far reaching consequences for health and disease. Specifically, a better understanding of NK cell activation may lead to novel immune based strategies to treat hematologic malignancies.